updated 11:13 p.m. ET Aug. 19, 2008

SAN DIEGO - Chargers tight end Antonio Gates was taken off the physically unable to perform list on Tuesday and participated in parts of practice after passing a physical.

Gates had surgery nearly six months ago to repair a tear in the plantar plate of his left foot. He injured his left big toe during a playoff game against Tennessee last January. He was placed on the PUP list in late July.

“Today was a pretty good day. I really pushed it. I gave it my all to see what I could do,” said Gates, a Pro Bowl selection each of the past four seasons.

He said his prospects look good for playing in the regular-season opener against the Carolina Panthers on Sept. 7, but only if he doesn’t have any setbacks with his foot.

“I hate to look so far down the road because this is a tricky situation,” Gates said. “It’s one of those things where it feels really good one day and you come back another day and it’s sore.

“It’s one of those injuries where you have to really monitor and make sure I’m not overdoing it.”

If Gates hadn’t passed a physical before the final roster cutdown on Aug. 30, he would have been required to miss the first six games of the regular season.

Defensive end Luis Castillo also returned to practice after missing most of the past two weeks due to back pain. Castillo signed a five-year, $43 million contract last month.

Pro Bowl linebacker Shawne Merriman (knee) missed both of Tuesday’s practices.

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